What is a glacier? Glaciers are large persistent bodies of ice that form over centuries of snow falling faster than it is melting. • They must be at least 0.1 km2 in area and 50m thick to be classified as a glacier. • They form what is known as the cryosphere, which is defined by the portions of the Earth where water is in solid form.
Where are they? Alpine glaciers are found in mountain ranges of every continent • Form on mountainsides and flow down to fill valleys (valley glaciers) • Found on every continent except Australia
99% of glacial ice is contained within vast continental glaciers in the north and south polar regions • The Greenland ice sheet covers about 82% of its surface • If melted, it would raise sea levels by 7 metres (23 feet) • Antarctica has the largest sheet of ice on Earth – 14 million km2 • Contains around 90% of Earth’s fresh water • If melted, it would raise sea levels by almost 70 metres (230 metres, or around 36 average women stacked from head to foot) • These are where icebergs come from (Calving)
How are they formed? • Accumulation of snow over a period of time • Compression of snow at the bottom – much like sedimentary rock • Pushes air out, making glaciers appear blue • Just like taking a handful of snow and squeezing it into a hard snowball, except a huge snowball. • http://www.youtube.com/watch?v=Cqgb2OZF2Zc&feature=related Glacier forming
They can move?! • Glaciers are the largest moving objects on earth. • Eventually, the snow gets so heavy that it starts to move like a river of ice. There are two ways glaciers can move: • Spreading occurs mostly with ice sheets. The glacier’s own weight becomes too much for it to support itself. It will gradually spread out like cookie dough baking in the oven. • Basal Slip occurs when the glacier rests on a slope. Pressure causes a small amount of ice beneath the glacier to melt, creating a thin layer of water. • This reduces friction enough that the glacier can slide down the slope.
They can also expand and contract leaving behind different landforms. • During the last ice age at the end of the Pleistocene era, giant glacial ice sheets extended from the poles to cover most of Canada -It has long since shrunk, but has left much evidence behind that we will explore in the “Landforms” unit.
So why do they matter? • Do you like to eat? • Irrigation for much of the world’s farmland comes from glacial runoff. • Do you like to drink water? • 79% of the Earth’s total supply of drinking water is frozen in glaciers. • Do you like electricity? • Glacial waters generate electricity by being channeled through hydro-electric turbines • Glaciers are essentially the canary of the global mine • You get to inherit these problems http://www.dailymotion.com/video/xnoaug_time-lapse-photos-show-stunning-glacial-erosion_news Canada glacial melt http://www.youtube.com/watch?v=aKoch_iEos8 Maldives video
What can we do? • http://www.youtube.com/watch?v=6dFbuaz130c Glacier making • http://videos.howstuffworks.com/science/project-earth-videos-playlist.htm#video-32591 Glacier wrapping • Brainstorm some ways we can help slow melting
Your Task • Read the article handout you are given. As a group, brainstorm answers to the questions below and then present to the class. • Briefly explain the situation • What is happening to the glacier/ice sheet? • How does this affect the environment? • How does this affect people? • What does this mean for the future?
Neat Facts • Glacial ice is the largest reservoir of freshwater on Earth and supports 1/3 of the population. • Siachen Glacier, a huge glacier in the Himalayan Mountains, is sometimes called the “Third Pole”. • 10% of Earth’s land is covered in glacial ice. • During the last ice age, glaciers covered 32% of total land area and 30% of the oceans. • The glaciers of Antarctica are so heavy they actually change the shape of the Earth. • Meltwater from glaciers along the Alberta–B.C. border ends up in all three of Canada’s oceans – the Pacific, the Arctic, and the Atlantic (through Hudson Bay). • Canada’s 200,000 square kilometres of glaciers and icefields would cover an area about half the size of Newfoundland and Labrador if put together. • After Antarctica and Greenland, Canada has more glacier ice than any other part of the world.
http://phet.colorado.edu/en/simulation/glaciers#software-requirementshttp://phet.colorado.edu/en/simulation/glaciers#software-requirements Interactive thing! • http://education.nationalgeographic.com/education/encyclopedia/glacier/?ar_a=1#page=2 National Geographic glacier pictures and explanations http://www.economist.com/blogs/dailychart/2011/09/melting-arctic-sea-ice-and-shipping-routes Northwest passage